Message Modification

Here we will show how to make a controlled modification to a given message, even if some (or all) of the original message is unknown.
Assume a message M was transmitted, and the ciphertext was C and the IV was v.
v and C are known to the adversary.
The adversary wants the 802.11 receiver to accept a fake message F = M XOR D for some D of his choosing.
D could be chosen to as to change a dollar amount in a funds transfer, for example, even if the entire message was not known
We use the fact that the CRC-32 is linear, and also that RC4 (like all stream ciphers) is also linear:
If C = RC4(v,k) XOR P, then
(C XOR D) = RC4(v,k) XOR (P XOR D)